Jebao powerhead mounting rubber coming off in my hand
 

I was cleaning my powerheads last night and noticed that mounting rubber is coming off on my hand when I handle it. When I rub it, it comes off in thick black goo.

Has anyone else noticed this? I wonder if this is leaching into the aquarium.

https://i.imgur.com/MgVRdD7.jpg?1

Had that happen once when I used bleach.

Yeah I could see that if bleach was used. I've never used bleach on them. I also remove the rubber when soaking the powerhead in vinegar water.

I'm wondering if it's something to due with carbon dosing. I dose vinegar.

I wouldn't put that in my tank? I have seen that with rubber and acetone but not with anything in and around the fish tank. It is likely just really cheap rubber/plastic.

I have some Jebao pumps that I use for backup but have not had that problem. I consider the pumps throw aways because they are so cheap.